供应链可追溯性的构建能够对食品安全问题进行溯源，因此对于降低食品安全风险来说非常重要。此外，它能够帮助监管者了解食品安全风险发生的供应链环节，并能够对上游农业企业的经济性动机掺假行为产生威慑。本文聚焦于中国水产品供应链，试图通过构建批发市场经营户、养殖户和政府三方的博弈模型和使用大规模的水产品批发市场实地调研数据，分析经营户可追溯采纳行为。该实地调研数据涵盖了浙江和湖南两省所有存在水产品交易的批发市场，具体来说，包含76家批发市场和763个经营户的信息。理论和实证研究的结果表明，批发市场经营户之间采用可追溯性与食品安全抽检强度、经营户个人的被抽检经历和风险意识密切相关；此外，在私营市场中，抽检强度对经营户的产品可追溯性采纳的影响要强于国家/集体所有权的市场。本文提供了关于中国水产品可追溯性发展的情况，更为重要的是，发现了可能影响批发市场经营户的产品可追溯性的因素，以期为相关政府部门促进水产品供应链的可追溯性提供建议。

Globally, white clover (Trifolium repens L.) is commonly infected by plant viruses.  It is grown at gardens, roadsides, and public areas as ornamental plants in northern China.  Some leaves present disease symptoms that are similar to those of virus infection.  However, to our knowledge, no records are available from China regarding white clover (Trifolium repens L.) virus co-infection.  To determine the viral species that infect white clover in China, plant samples with virus disease symptoms were collected and virion morphology and ultrastructure morphology of co-infected plants were observed by electron microscopy; viruses were detected by enzyme linked immunosorbent assay (ELISA) and reverse transcription PCR (RT-PCR).  Virus co-infection was studied by double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) and real-time fluorescence quantitative PCR (RT-qPCR) after rub-inoculation of virus-free white clover planted in a growth chamber (25°C) with a photoperiod of 16 h, using single or several purified virions.  Results showed that there were six types of symptoms, including those of shrinking mosaic, shrinking and macular mosaic, severe mottle mosaic, yellow macular mosaic, shrinkage chlorisis, and ring plaque and ring stria.  The incidence rates for each symptom were 20.93, 1.48, 16.85, 59.07, 1.30, and 0.37%, respectively, based on the field investigation.  Two types of viral pathogens were identified as Alfalfa mosaic virus (AMV) and White clover mosaic virus (WCMV).  In mesophyll cells, virus particles with bacilliform virions formed aggregates and linear virions were bundle shaped.  The detection rate of AMV was 100% in white clover samples by DAS-ELISA and RT-PCR detection, whereas that of WCMV was 83.33%.  The co-infection rate was 83.33%.  The relative contents of AMV and WCMV were significantly increased by 5.897- and 3.515-fold upon co-infection, when compared to that with single virus infection.  We observed larger starch particles and fewer or collapsed chloroplast grana in co-infected plants; in addition, vacuoles were twisted and smaller, compared to those of healthy plants.  To our knowledge, this is the first report of co-infection by AMV and WCMV in white clover, which has caused severe mosaicism and ultrastructure lesions in co-infected plants in China.

Food safety issues constitute an international topic discussed by many scholars. Although there is an extensive body of literature on comparisons of food safety control practices across different governance structures, these studies have been conducted mainly in terms of qualitative and descriptive analysis. In addition, little attention has been given to family farms. This study addresses the food safety control practices adopted by firms with different governance structures in China. Food safety control is expressed by the following aspects, i.e., pollution-free, green, organic, and/or geographical indication products certification, establishment of production records, and pesticide residue testing. Three types of governance structures that engage in agricultural production are distinguished: farmer cooperatives, agricultural companies, and family farms. The food safety control practices of various governance structures are investigated based on a database that comprises 600 vegetable and fruit enterprises in Zhejiang, China. The results show that (1) pesticide residue testing is adopted by the most firms, followed by products certification, and production records are adopted by the fewest firms, and (2) agricultural companies adopt more food safety control practices than family farms, while farmer cooperatives adopt the fewest food safety control practices. Governance structure features of a cooperative in terms of ownership, decision-making, and income distribution are the main reasons for the low level of food safety control in the cooperative.